Currently conventional frac plugs have to be milled/cut out after a well is hydraulically fractured. This can be very costly and it also restricts the depth at which plugs can be used. Plugs themselves can be run out to very long distances; however, such plugs cannot be easily milled/cut out after being set because coil tubing or other drilling/milling means can only extend out so far in a horizontal well.
There is also an issue with the amount of water it takes to pump a plug in a horizontal or directional well to its destination.
Dissolvable plugs and balls are available, but conventional technology is not reliable. A portion of the balls/plugs dissolve, but often they don't completely dissolve and they end up causing a restriction in the wellbore. Operators are often required to go back into a well and run a mill/cleaning trip to remove debris left by such dissolving plugs. This negates the benefits of running the dissolvable plug in the first place.
The present invention (“Adaptive Seat”) also referred to as adaptive seal, or plainly the seat comprises a simple sealing seat and dart/ball designed to replace a conventional frac plug. The present invention is designed so that it can be deployed into the inner bore of a liner system and support a dart, ball or other dropped object. Once the dart/ball/object lands on the seat, it seals off the portion of the wellbore below the seat and makes it possible for the zone above the seat to be hydraulically fractured. Typically, a composite plug made up of many parts is used to accomplish this task. By contrast, the adaptive seat which is a relative simple low cost item of unitary construction that can be used instead of the costly composite frac plug.
The adaptive seat can be deployed using a conventional wireline or pipe-conveyed setting tool. The setting tool can be easily retrofitted by removing certain parts from its lower end and replacing them with components that allow the seat to be deployed in a well. Once deployed, the adapter kit for the seat has a collet mechanism that holds the adaptive seat in place while a mandrel adapter pushes the seat into position. Once the seat is in position, an observable pressure/tension increase is visible at surface to let an operator know the seat has been set within a wellbore.
The seat does not have any issues running downhole or in a horizontal well since it doesn't have any packer/rubber elements on it. As such, the bottom hole assembly for the seat can be run into a wellbore and set very quickly, up to two to three times faster than conventional frac plugs.
The seat design has a large internal diameter (ID), including after it is set in casing. The seat will not need to be milled out. The dart/ball/object is constructed of dissolvable material so it does not have to be milled out either.
In one embodiment, the adaptive seat is run in conjunction with a dart/ball that has a slight taper which will help the adaptive seat seat/set. The harder you pump on the dart the more it pushes the seat radially outward into the casing which insures said seat is fully set.
The seat is designed to handle high amounts of stress while it is coiled into a small adaptive seat and expand out into a recessed area when relaxed or against a support in a tubular passage. This can be done by optionally cutting the outside diameter and the inside diameter of a square or circular seat such that the high stresses in the outside diameter and inside diameter of the seat are removed and the seat is free to open out to its uncompressed size from very small diameters.
The dart/ball supports the seat in its groove and makes it impossible for the seat to come out of the groove. It can be designed with a taper which lands in the inside diameter of the seat and pushes the seat out into the groove. Additionally or alternatively, the seat can have a bevel or chamfer for the same purpose. The seat can have a seal on the front of it to help it seal against the seat so the seat doesn't have to be designed with a seal on it. Alternatively, the seat can seal using a metal-to-metal seal.
A conventional setting tool can be used to easily deploy the adaptive seat. It's designed with a collet assembly to hold the seat from getting cocked in the inside diameter of the casing. Once the setting tool pushes the seat down to a groove in the casing, a pressure increase will be observable at surface allowing the operator to stop operations and retrieve the setting tool.
The adaptive seat removes the need to run a costly composite frac plug. Having a single part greatly reduces cost and failure modes. It can be run out to any depth since it does not have to be milled up later.
The seat also has a very large inside diameter, even when it's set into a groove in a wellbore. This makes it possible to leave the seat in a well and not have to go back and mill it out.
A dart/ball is used in conjunction with the seat. The interface between the dart and the seat make the seat much less likely to collapse and not likely to come out of the groove. Having a taper on the dart or seat also allows the dart to apply additional forces on the seat such that it will aid the seat in staying in the groove under high pressures typically observed during a hydraulic fracturing operations.
Modifying the outside diameter and the inside diameter of the seat with small gaps or cuts, it is possible to decrease the stresses in the seat and make it possible to “roll” up the seat into a small cylinder and then knock it out of its cylinder so that it opens up radially outward. This makes it possible to land said seat into a groove in the inner surface of the wellbore. It sticks out in the inside diameter just enough to catch the dart/ball and its inside diameter is large enough that small diameter composite plugs can be run through it if needed. A composite plug can still be used as a contingency if there's an issue with the seat or the casing. The large inside also leads to composite plugs being run through it for re-fracs later in the well's life.
The seat of the present invention is a single item, very cost effective, and simple to deploy, there is no need to go back and mill/cut up a plug. Frac plugs can be run through it if needed. Those skilled in the art will more readily appreciate these and other aspects of the present invention from a review of the description of the preferred embodiments and the associated drawings while appreciating that the full scope of the invention is to be determined from the appended claims.
As set forth above, an Adaptive Seat can be deployed into a landing sub, and a ball or dart is dropped down hole and seals against the Adaptive Seat in order to form a wellbore barrier, and to stimulate zone(s) above said ball or dart. In an alternative embodiment of the present invention, said landing sub's nipple profile for the Adaptive Seat is designed to support a seated ball when fluid pressure is applied above the ball, yet “un-support” the Adaptive Seat when fluid pressure is applied from below said ball. Said alternative embodiment makes it possible to flow the balls back to surface after all zone(s) above the ball are stimulated or otherwise treated. Further, conventional composite type balls can be utilized with said alternative embodiment, wherein said conventional balls can be flowed back to the surface without the need for milling of said balls or other downhole barriers.
Additionally, in yet another embodiment of the present invention, said balls can be flowed back or circulated toward the surface of a wellbore and land on another seat (supported), but not seal with said seat (or, more specifically, a ball-seat interface). In one embodiment, a ball has a shoulder on one side which is fluted to allow fluid flow from below the ball to flow around and through said flutes on the upper side of the ball. Said ball can be designed with many obstructions to keep it from landing on a seat when flowing back within a wellbore.